Stretched surface recording disks (SSR) generally consist of a rigid, circular support and a thin polymer film suitably attached to the periphery of the support. The disk configuration allows random access to different portions of the recorded information, since all the information is available on a single plane, thus overcoming the main shortcoming of linear tape systems in which information is located in widely separated portions of the tape requiring relatively large amounts of time in unwinding and rewinding the tape for access. SSR can be made two-sided and they can be stacked to allow random access to information on multiple surfaces.
SSR are shown in U.S. Pat. No. 2,662,804 (Hutton); U.S. Pat. No. 3,130,110 (Schmidt); U.S. Pat. No. 3,336,583 (Comstock); and U.S. Pat. No. 3,488,646 (Sugaya). The development of SSR has progressed over the years from a rather simple configuration described in U.S. Pat. No. 3,373,413 (Treseder) in which a film was stretched and clamped between two circular rings, to a dish-shaped support to which a stretched film was attached at the periphery as illustrated by U.S. Pat. No. 3,509,274. Subsequently, U.S. Pat. No. 3,537,083 introduced the concept of bonding the film at the center of the support in addition to the support periphery, and U.S. Pat. No. 3,599,226 described an SSR which included two stretched film surfaces, one on either side of the support, which were attached at the periphery and near the center of the support.
U.S. Pat. No. 4,328,607 shows a drum head-like recording medium wherein the recording sheet has a metal foil backing.
SSR are superior to floppy disks in that a pressure-pad is not required, and the recording surface has substantially the same dimensional stability as the relatively massive base to which it is attached. In addition, the SSR provides a flat recording surface which may be deformed slightly to conform to a transducer head and irregularities in the surface of the head.
Although the patents described above have illustrated the general configuration and certain desirable features of SSR, practical problems remain as impediments to the mass production and general acceptance of SSR. These include the problem of economically and reliably attaching the very thin recording medium film to a relatively thick support, ensuring that the film remains at desired tension and planar with respect to the support.
The bonding of the magnetic recording sheet to the support of an SSR should satisfy the following criteria: a. high shear strength to withstand the tension of the stretched medium; b. minimal creep between recording medium film and support to maintain data track stability; c. smooth bonding surface to provide a smooth recording surface; and d. short setting time to allow for high production volume.
Various means have been examined for bonding magnetic recording media film, the underside of which is typically polyethelyene terephthalate, to supports of various materials (i.e. metals, plastics, composites). Pressure sensitive adhesives generally do not meet the shear and creep requirements. Thermoplastic adhesives require heat for bonding and may have viscosities which are too high to give a smooth bond surface. Thermosets (e.g., cyanoacrylate or epoxy adhesives) have setting times which are difficult to control.